In manufacturing a semiconductor device, various processes, such as a film formation process or an etching process, are repeatedly performed on a semiconductor wafer in order to manufacture a desired device. Recently, a resistance reduction (improvement of conductivity) of a wiring and an improvement of an electro-migration resistance have been required in order to cope with requirements for speeding-up, finer-patterning of a wiring, and a high integration of a semiconductor device.
In order to cope with such requirements, Cu has been used as a wiring material. Cu is high in conductivity (low in resistance) and excellent in electro-migration resistance as compared to aluminum (Al) or tungsten (W).
As a Cu wiring forming method, a technique has been proposed, which includes: forming a barrier film formed of tantalum (Ta), titanium (Ti), a tantalum nitride (TaN), a titanium nitride (TiN), or the like through plasma sputtering, which is a Physical Vapor Deposition (PVD) method, over the entire interlayer insulating film in which a trench or a hole is formed; forming a Cu seed film on the barrier film also through plasma sputtering; performing a Cu plating processing thereon to completely embed the trench or the hole; and polishing a superfluous copper film and a barrier film on the surface of the wafer through a Chemical Mechanical Polishing (CMP) processing to remove the copper film and barrier film.
Meanwhile, as the wiring pattern is made further finer, it becomes difficult to obtain sufficient step coverage when a barrier film formed through the PVD method as described above is used. Thus, recently, a manganese oxide (MnO)x film formed by a Chemical Vapor Deposition (CVD) method or an Atomic Layer Deposition (ALD) method, which is capable of forming a thin film with a good step coverage, has been reviewed as a barrier film. However, since the MnOx film has poor wettability with Cu, there has been proposed a method of forming a Cu wiring by forming a ruthenium (Ru) film, which has good wettability with Cu, on the MnO film and then forming a Cu film thereon.
However, since the nuclear forming density of Ru is low when the Ru film is formed on the MnOx film, it is difficult to obtain a Ru film with a good surface condition. Therefore, there has been proposed a technique that performs a hydrogen radical processing after forming the MnOx film, and then forms a Ru film.
In the case of forming a Ru film on a MnOx film, the Ru film also needs to be removed through the CMP processing. However, since Ru is highly stable, it is very difficult to perform the CMP processing on Ru. For this reason, an electric characteristic may be deteriorated by a polishing residue containing Ru, or a Cu wiring may be corroded by a specific chemical liquid used when removing Ru. Thus, a product yield may be reduced.